GI drugs in Horses
Terms
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- Xylazine
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alpha- 2 agonist
sedation
analgesia
Use: colicky horse
esophageal obstruction - detomidine
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alpha- 2 agonist
sedation
analgesia
Use: colicky horse
esophageal obstruction - butorphanol
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opioid
analgesia
CNS stimulation?
Use: GI pain
Post-op colic - Lidocaine
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local anesthetic
anti-arrhythmic
analgesic
anti-inflammatory
prokinetic effects
Toxicity: muscle fasciculations, ataxia, collapse, seizures
Interacts with: cimetidine, metronidazole (both use hepatic cytochrome P450)
Used for: post-op, ileus, and proximal enteritis - Caudal epidural anethesia
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used for correction of rectal prolapse.
Not common
use xylazine and/or lidocaine
and morphine - Flunixin meglumine
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NSAID
analgesic, anti-pyretic, anti-inflammatory effects, anti-endotoxic
Most commonly used NSAID for GI problems - Ketoprofen
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NSAID
analgesic, anti-pyretic, anti-inflammatory effects
anti-endotoxic
Less ulcerogenic
more expensive
used mainly in foals. - Phenylbutazone
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NSAID
analgesic, anti-pyretic, anti-inflammatory effects
not as effective for acute abdominal pain
mainly used for musculo-skeletal pain (laminitis)
May be better stopping ileus from endotoxins than flunixin - Hyperimmune plasma (J5plasma)
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anti-endotoxic
provides small amount of proetina and other plasma factors such as ATIII.
really expensive - Polymyxin B
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anti-endotoxic
binds lipid A portion of endotoxin
side effects: nephrotoxicity and neurotoxicity
Need to make sure animal is rehydrated before administering - Pentoxifylline
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anti-endotoxic (rhealogic drug)
Synthetic xanthine derivative
phosphodiesterase inhibitor
Decreased bioavailability after repeated dosing, so may need to increase the dose as the problem continues - Dimethylsulfoxide (DMSO)
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anti-endotoxic
radical scavenger,
anti-inflammatory effects
causes hemolysis if given too fast or too much - Anti-endotoxic drugs
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Best if given before exposure
use for: grain overload, strangulating intestinal obstruction
colitis
peritonitis
post op ileus - Bismuth subsalicylate (peptobismol)
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Intestinal protectant
adsorbs toxins
provides protective coating to inflamed mucosa
mild antibacterial action
anti-diarrheal agent
- careful that foals don't get constipated!
4 x daily - Kaolin pectin (Kaopectate)
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adsorbs toxins
anti-diarrheal agent
questionable efficacy
2 X daily - Activated charcoal
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Intestinal protectant
adsorbs certain toxins and drubs
prevents or reduces their systemic absorption
may give laxative 30 minutes later to move toxins out faster
Dairy products and mineral oil decrease effectiveness
give oral meds at least 3 hours before or after to reduce interference - Magnesium sulfate (Espom salt)
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laxative/cathartic
osmotic agent
draws water into GI lumen
interferes with tetracycline products
do not use more than 3 days in a row due to Mg toxicity or enteritis - Dioctyl sodium succinate (DSS)
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laxative/cathartic
Surface-acting agent
Stronger, but has more side effects (abdominal discomfort, intestinal irritation, dehydration) - Mineral oil
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laxative/cathartic
lubricant
coats fecal material and mucosa
prevents reabsoprtion of water
mild laxative effect
causes severe granulomatous
pneumonia if aspirated
doesn't dissolve fecal ball, just lubes it.
good for ascarid impaction - Psyllium
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Laxative (bulk forming)
can be given as a top dressing on food as a preventative
usually used for sand impactions
also for chronic diarrhea - Water
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laxative/cathartic
softens stools and increases fecal mass
isotonic fluids may be better
as hyponatremia may develop -
Laxatives/Cathartics
indications: -
simple impaction colic (large or small colon)
grain overload
toxin ingestion
ascarid impaction (mineral oil)
sand impaction or chronic diarrhea (psyllium) - Aluminum/Magnesium Hydroxide (Maalox)
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Anti-ulcer medication
rapidly neutralizes acid (antacid)
short duration of action (give 4-6 times daily)
possibly preventive, not curative for gastric ulcers
Not used often - Cimetidine (tagamet)
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alpha 2 antagonist
effective in healing gastric ulcers
microsomal effects (at least in small animals)
can be given IV
given 4 X daily - Ranitidine (Zantac)
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Anti-ulcer medication
alpha 2 antagonist
effective in healing gastic ulcers
less microsomal effects than Cimetidine (at least in small animals)
can be given IV - Omeprazole (Gastrogard)
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Irreversible H+/K+ ATPase proton pump inhibitor (at luminal surface)
inhibits bot gastric volume and acidity
Long duration of action
can be used as a preventative
Used often
Can't be used in foals less than 4 weeks of age
Adverse effects uncommon (SIBO or Achlorhydria)
Use with severe mucosal disruption in small animals. - Sucralfate (Carafate)
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Anti-ulcer medication
sulfated pollysaccharide that coats ulcerated mucosa
Stimulates mucus secretion and increases PGE synthesis
Useful in combo with H2 antagonists (Cimetidine/Ranitidine) or antacids.
Coats well
Will be effective in an alkaline environment!
Small animals:
1. aluminum salt which binds to ulcers to form a physical barrier
2. inhibits pepsin, binds bile salts
3. increased cytoprotection -PGE
4. Acts locally only
5. interferes with drug absorption so give either 1-2 hours prior to other drugs. - Erythromycin lactobionate
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Prokinetic
Macrolide antibiotic with motilin receptor agonism
Acts on stomack, ileum, cecum and pelvic flexure
Side effects: abdominal pain and diarrhea
Given slowly IV every 6 hours - Cisapride (propulsid)
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Benzamide
Prokinetic
Increase ACh release at myenteric plexus
Promotes generalized increase in progressive motility (esophagus --> large colon)
can be mixed with erythromycin
No anti-dopaminergic (extrapyramidal) CNS side effects like metoclopramide does
small animals: can cause gastric retention and constipation - Bethanechol chloride
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prokinetic
synthetic muscarinic cholinergic agonist
promotes gastric emptying and mild cecal and colonic contractions
most commonly used with bladder problems
cost prohibitive in all abut the foal
overdose causes salivation, lacrimation, urination, defecation - Neostigmine methylsulfate
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prokinetic
Acteylcholinsterase inhibitor
Promotes cecal and large colon motility
start with small dose and increase gradually - Butylscopolammonium
- antispasmodic
- Metronidazole
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Antimicrobial (an azole)
good for clostridial diarrhea and enterotoxemia - Oxytetracycline
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antimicrobial
indicated for treatment of colitis due to Potomac Hose Fever
Give 3-5 days IV slowly - Erthyromycin
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antimicrobial (macrolide)
Used for proliferative enteropathy (lawsonia intracellularis) in weanling foals (this is cyclic... hits about every 5 years)
Also used for Pyogranulomatous enterocolitis caused by rhodococcus equi (Clarithromycin is more effective, but is Expensive, so this is the next best choice) - Chloramphenicol
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antimicrobial
Used in the treatment of proliferative enteropathy (Lawsoina intracellularis) in weanling foals that get diarrhea while taking erythromycin - vomiting
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1.common sign
2. differentiate from regurgitation
3. reflex act = neural activation
4. Receptors/Afferent pathways
a. abdomina viscera
b. chemoreceptor trigger zone
c. CNS
d. Vestibular system
Metabolic consequences:
dehydration, prerenal azotemia, electrolyte distubances (Na,K, Cl), acid base disturbances - Anti-emetics: when to use?
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patient distress (failure to rest)
hydration/electrolyte disturbances - Phenothiazine derivatives
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1. good broad-spectrum antiemetic
2. inhibits neural transmission in vestibular center (VC?)
3. possesses weak anticholinergic activity
4. Inhibits neural activity in CTZ
5. effective as low doses
6. hypotension and sedation are side effects - Antihistamines
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antiemetic by blocking H1 receptors in CTZ and Vestibular apparatus
Good for motion sickness and vestibular disorders.
Not commonly used
hypotension is a side effect - Dopaminergic antagonists
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anti-emetic that acts at CTZ on toxin and agents in blood
promotes gastric emptying by inhibiting GI myoelectric activity
good for Chemotherapy induced vomiting where anticholinergics are of little value.
Examples: metoclopramide and domperidone - metoclopramide
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1.anti-emetic good for chemotherapy induced vomiting
2.prokinetic drug
3. increase absorption vie incrase ACh release - domperidone
- anti-emetic good for chemotherapy induced vomiting
- Antiemetic summary
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Phenothiazines are good first choice as they have broad spectrum and can be given parentally
If they don't work, try a broader spectrum - Antibiotics
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Not commonly required for GI problems
1. used if there is severe mucosal injury such as with parvo, HGE, or salmon poisoning disease, hemorrhagic diarrhea, sepsis and neutropenia
2. Or with salmonella, campy, and clostridia
3. consider effects on host microflora and host immunocompetance. - Antibiotics side effects
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1. disruption of normal microflora
2. diarrhea due to ampicillin, tetracycline, and neomycin
3. prolongation of the carrier state if have Salmonella
4. aminoglycosides cause renal/systemic toxicity
5. Antibiotic resistance issues - Motility modifiers
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1. opioids are most effective
2. enhance segmentation, but decrease peristalsis
3. reduce intestinal secretions reserved for short-term use ONLY!
4. may cause CNS depression in cats.. AVOID!
5. do not use with invasive bacteria - anticholinergic drugs
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1. Not for use in dogs/cats with diarrhea
2. decrease tone and propulsion
3. may precipitate ileus (SIBO, toxemia, colonic secretions)
4. diarrhea reduces both segmentation and peristalsis therefore intestinal transit is rarely increased.
5. examples: atropine, glycopyrrolate - Antacids
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1. transiently neutralize HCl
2. have to be given often which leads to poor client compliance.
3. can cause acid-rebound (hypergastrinemia)
4. Ca++ salts can lead to constipation
5. Mg salts can lead to diarrhea
6. THEREFORE, NOT RECOMMENDED